1. Field of the Invention
The present invention relates to a television tuner unit having: a tuner for frequency-converting a received television signal into an intermediate frequency signal; a video intermediate frequency circuit part for detecting the intermediate frequency signal and outputting a video signal and a sound signal; and a stereo demodulator for demodulating a composite signal outputted from the video intermediate frequency circuit part and outputting a stereo sound signal.
2. Description of the Prior Art
FIG. 2 is a plan view showing a circuit layout of a conventional television tuner unit (hereinafter simply referred to as a tuner unit). A rectangular metal frame 11 has opposite long sides, a first side 11a and a second side 11b, and opposite short sides, a third side 11c and a fourth side 11d. A connector 12 through which television signals are inputted is attached to the third side 11c. The metal frame 11 is partitioned to first to third regions 11e, 11f, and 11g in this order from the third side 11c toward the fourth side 11d. In the regions 11e, 11f, and 11g, wiring boards (not shown) for forming circuits are respectively mounted.
In the first region 11e, a tuner 13 is formed which frequency-converts a received television signal into an intermediate frequency signal. The tuner 13 has an antenna tuning circuit 13a, a high-frequency amplifier circuit 13b, an interstage tuning circuit 13c, a composite IC (integrated circuit) 13d, a resonance circuit 13e, and an intermediate frequency tuning circuit 13f, and the like. The high-frequency amplifier circuit 13b is configured with a variable gain amplifier, and the composite IC 13d is configured with a mixer transistor, an oscillator transistor, a PLL circuit for selecting channels, and the like (not shown). The resonance circuit 13e is coupled to the oscillator transistor within the composite IC 13d to make up an oscillator.
In the second region 11f, a video intermediate frequency circuit part 14 is formed which detects an intermediate frequency signal and outputs a composite signal of a video signal, a sound signal, and stereo, and generates an AGC voltage. The video intermediate frequency circuit part 14 has a SAW filter 14a, a video intermediate frequency IC 14b including a video detector and an intermediate frequency amplifier (not shown), a voltage controlled oscillator 14c, a trap circuit 14d, and the like. The voltage controlled oscillator 14c is used to detect video.
In the third region 11g, a stereo demodulator 15 is formed which outputs a stereo sound signal from a composite signal outputted from the video intermediate frequency circuit part 14. A major portion of the stereo demodulator 15 is configured with integrated circuits.
The first side 11a is provided with plural terminals 16 that are respectively connected to the tuner 13, the video intermediate frequency circuit part 14, and the stereo demodulator 15. When the tuner unit is mounted on a mother board (not shown) on which television set main circuits are formed, the terminals 16 are inserted in the mother board and connected to the circuits.
The first side 11a corresponding to the first region 11e is provided with terminals related to the operation of the tuner 13 such as an AGC voltage input terminal (AGC) 16a, a PLL circuit address terminal (AS) 16b, a clock terminal (CL) 16c, a data terminal (D) 16d, a power terminal (B) 16e, a tuning voltage source terminal (TU) 16f, and the like.
The AGC terminal 16a is connected to the high-frequency amplifier circuit 13b; the address terminal 16b, clock terminal 16c, and data terminal 16d are connected to the composite IC 13d; the power terminal 16e is connected to the high-frequency amplifier circuit 13b and the composite IC 13d; and the tuning voltage source terminal 16f is connected to the composite IC 13d. 
The first side 11a corresponding to the second region 11f is provided with terminals related to the operation of the video intermediate frequency circuit part 14 such as a power terminal (B) 16g, an AGC voltage output terminal (AGC) 16h, a video signal terminal (V) 16i, a sound signal terminal (A) 16j, and the like. The power terminal 16g and the AGC voltage output terminal 16h are connected to the video intermediate frequency IC 14b, and the video signal terminal 16i and the sound signal terminal 16j are connected to the trap circuit 14d. 
The first side 11a corresponding to the third, region 11g is provided with a power terminal (B) 16k, a right sound signal terminal (R) 16l, and a left sound signal terminal (L) 16m that are connected to the stereo demodulator 15.
From a power supply part of the television set body, a power supply voltage is applied to the three power terminals 16e, 16g, and 16k through which it is supplied to corresponding circuits. This prevents a power supply line within the tuner unit from becoming long. Also to the tuning voltage source terminal 16f, a voltage (30 V) is supplied from the power supply part of the television set body. This voltage serves as a voltage source for generating a tuning voltage for selecting a channel, and the tuning voltage is set based on a signal related to channel selection, inputted to the address terminal 16b, clock terminal 16c, and data terminal 16d. The set tuning voltage is supplied to the antenna tuning circuit 13a and the interstage tuning circuit 13c. 
A video signal and a sound signal of a selected channel are outputted to the video signal terminal 16i and the sound signal terminal 16j, respectively. For stereo broadcasting, a stereo sound signal is outputted to the right sound signal terminal (R) 16l and the left sound signal terminal (L) 16m. An AGC voltage outputted to the AGC voltage output terminal 16h is inputted to the AGC voltage input terminal 16a again via the mother board and supplied to the high-frequency amplifier circuit 13b. 
With the structure of conventional tuner units, circuits (tuner, video intermediate frequency circuit part, and stereo demodulator) are disposed in the horizontally extending region, the first region to third region, increasing a mounting area on a mother board of the television set body. Also, the three power terminals are provided because of the long disposition of the circuits, increasing the number of terminals. Moreover, the two AGC terminals are provided to supply an AGC voltage generated in the video intermediate frequency circuit part to the high-frequency amplifier, increasing the number of terminals.